(1) Field of the Invention
The present invention relate s genera lly to improvements in the construction of metal frame buildings, and in particular to improvements in the attachment of metal frame building components.
(2) Description of the Prior Art
Residential and commercial buildings historically have been constructed of a wooden frame formed of lumber components that have been nailed to each other to form the desired structure. While this technique is still used in the majority of residential buildings, there has been a trend toward replacement of the wooden framing members, either partially or entirely, with metal framing components. This trend is due to several factors, including the ease of handling, the availability of wood, fire resistance and, particularly in coastal areas, the need for buildings that will withstand high wind forces.
Generally, these metal frames are constructed with elongated hollow metal framing members having dimensions equal to standard lumber dimensions of 2.times.4s, 2.times.6s and 2.times.8s as substitutes for conventional wooden lumber. It will be understood by one skilled in the art that lumber dimensions are not the same as inches. For example, a 2.times.4 is actually 1.75 inches.times.3.5 inches. However, standard lumber dimensions will be used herein for convenience.
Major framing components, such as I-beams, are usually joined by welding. Some framing components are welded or bolted to a common plate. Many metal framing components, however, are normally attached with screws. Usually, the end of one component is inserted into a recess between two walls of another component and a plurality of screws are inserted through abutting walls of the two components. For example, in the construction of a metal frame wall an elongated, channel-shaped connector plate or beam having a horizontal bottom wall and upright side walls extending upwardly from the edges of the bottom wall is secured to the building floor or foundation.
The lower ends of a plurality of evenly spaced C-shaped studs are then mounted vertically in the plate, resting on the bottom wall. Each stud has a side wall and opposed end walls that abut the inner surfaces of the beam side walls when the stud is in position. Metal screw are then inserted from the exterior of the beam through the beam side walls and the abutting stud end walls to secure the studs to the beam.
This procedure is described, for example, in U.S. Pat. No. 4,619,098 to Taylor. U.S. Pat. No. 5,596,859 to Horton et al., while primarily concerned with the attachment of metal studs to wooden base plates, mentions that a metal plate can be used, with the stud and metal plate being joined by self-tapping screws. U.S. Pat. No. 5,440,848 to Deffet also describes attachment of a metal studs, but is concerned only with nailing to wooden attachment plates.
Other techniques have also been described in the prior art for attaching two metal building framing components. For example, U.S. Pat. No. 4,854,096 to Smolik utilizes spaced cut-outs, or "fingers," that extend inwardly from the side walls of the attachment plates, with the stud being inserted between the cut-outs. U.S. Pat. No. 5,222,335 to Petrecca and U.S. Pat. No. 5,394,665 to Johnson describe metal frame constructions using inwardly directed projections on the attachment plate side walls that mate with corresponding indentations on the stud end walls.
Prior art techniques, such as those described above, may be somewhat easier to use than screws. However, the strength of the attachment is mainly the result of friction, and thus is of little strength. Therefore, the utility of these techniques is essentially limited on interior, non-loading bearing circumstances. As noted in the above Petrecca patent, the only purpose for screws in an interior non-load bearing wall is to hold the studs in a vertical position until the dry wall is applied.
These techniques are not sufficient, however, for attachment of metal framing components in other parts of the building construction, either on the exterior of the building or the building interior, where load-bearing members are required, or where the structure is subjected to stress. Thus, there remains a need for a means of attaching metal frame building components that will withstand load-bearing forces and stresses.